By simplifying and limiting current circuit model of metro power supply, this paper firstly showed stray current production and its damage, then analyzed bilateral power supply system using resistor network theory, and constructed stray current analytical model of bilateral power supply, computer simulation in different conditions of stray current distribution was carried out, the results show that metro stray current is affected by substation pitch, railway portrait resistor, rail-to-ground transition resistor and other factors, the distribution of stray current is provided macroscopicly in a qualitative way. This gives theoretical basis on how to set the distance of substation. Ultimately it provides a good solution to reduce the stray current corrosion.